Pathways for Improving the Photovoltaic Efficiency of Porphyrin and Phosphorene Antidot Lattice Nanocomposites: An Insight from a Theoretical Study

The porosity of a newly synthesized phosphorene antidot lattice (PAL) is promising for encapsulating the porphyrin molecule and thus shows a versatile route to fabricate porphyrin/PAL nanocomposites. We herein explored the photovoltaic performance of a tetraphenylporphyrin (TPP)/PAL composite system. Interestingly, TPP/PAL composites show type-II staggered band alignment where a conduction band resides on TPP and a valence band resides on PAL. However, the driving force for hole transfer to PAL from TPP is very small (similar to 0.02 eV), implying faster charge recombination inside the TPP itself. To overcome the unpleasant situation, we adopted a substitution strategy at TPP and PAL components. As porphyrins are effective photosensitizers due to the pi-conjugated electronic structure, we attached an electron-donating group (-NH2) to the TPP moiety and an electron-withdrawing group (-CN) at the edge of PAL. The composites show a high photovoltaic performance of up to 13.5%, making them competitive with other two-dimensional heterostructural solar cells. Interestingly, if the starting material is TiO-TPP instead of TPP, then one may achieve the intended type-II band alignment and open up a new route to improve the efficiency without functionalizing the TPP or PAL.